mailsync: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/mailsync - from package: mailsync

You may install the required package with command apt-get install {package}

Error in other languages:
mailsync: bevel nie gevind nie
mailsync: comandă negăsită
mailsync: comando não encontrado
mailsync: commande introuvable
mailsync: command not found
mailsync: käsku ei ole
mailsync: không tìm thấy lệnh
mailsync: komanda nerasta
mailsync: Kommando nicht gefunden.
mailsync: kommandot finns inte
mailsync: komut yok
mailsync: nie znaleziono polecenia
mailsync: níor aimsíodh an t-ordú
mailsync: no se encontró la orden
mailsync: no s'ha trobat l'ordre
mailsync: opdracht niet gevonden
mailsync: parancs nem található
mailsync: perintah tidak ditemukan
mailsync: príkaz nenájdený
mailsync: příkaz nenalezen
mailsync: команда не найдена
mailsync: командата не е открита
mailsync: 命令找不到
mailsync: コマンドが見つかりません